Method and system for time constant for a 3D comb filter

ABSTRACT

Methods and systems for time constant for a 3D comb filter of a video signal are provided. Aspects of the method may include assigning a weight to a 3D comb mesh value. Combing may be blended according to the assigned weight of the 3D comb mesh value. The weighted 3D comb mesh value may be accumulated in order to generate accumulated mesh value. If the accumulated mesh value exceeds a saturation value, the accumulated mesh value may be reduced to the saturation value. If the 3D comb mesh value is smaller than a first threshold value, the accumulated mesh value may be reset to zero. A multiplier may be generated according to the accumulated mesh value. If the accumulated mesh value is between a second threshold value and a third threshold value, the multiplier may be blended.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This patent application makes reference to, claims priority to andclaims benefit from U.S. Provisional Patent Application Ser. No.60/540,890, entitled “METHOD AND SYSTEM FOR TIME CONSTANT FOR A 3D COMBFILTER,” filed on Jan. 30, 2004, the complete subject matter of which ishereby incorporated herein by reference, in its entirety.

This application makes reference to:

-   U.S. application Ser. No. 10/943,267-   filed Sep. 17, 2004;-   U.S. application Ser. No. 10/943,587-   filed Sep. 17, 2004;-   U.S. application Ser. No. 10/943,593-   filed Sep. 17, 2004;-   U.S. application Ser. No. 10/943,596-   filed Sept. 17, 2004;-   U.S. application Ser. No. 10/869,395-   filed Jun. 16, 2004; and-   U.S. application Ser. No. 10/943,641-   filed Sep. 17, 2004.

The above stated applications are hereby incorporated herein byreference in their entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to processing of videosignals. More specifically, certain embodiments of the invention relateto a method and system for time constant for a 3D comb filter of a videosignal.

BACKGROUND OF THE INVENTION

A composite video signal is the sum of a luminance (brightness) signaland a chrominance (color) signal. These signals may be referred to asluma and chroma signals, respectively. The frequency ranges of the lumaand chroma signals are designed to overlap. In video processing, theluma and chroma signal components are added together in order togenerate a composite video signal. The luma and chroma video elementsare integrated and broadcasted as a single composite video stream. Oncethe broadcasted composite signal is received, the luma and chroma signalcomponents must be separated in order for the video signal to beprocessed and displayed. A comb filter may be utilized for separatingthe chroma and luma video signal components. For example, a televisionmay be adapted to receive a composite video input and utilize anintegrated comb filter to separate the chroma and luma video signalcomponents. However, before the television can display the receivedvideo signal, the chroma and luma video components have to be separated.

FIG. 1 is a diagram illustrating generation of a conventional compositevideo signal. Referring to FIG. 1, a conventional composite video signal105 may be generated from a luma component 103 and a chroma component101. The composite video signal 105 may be generated by adding thechroma video signal component 101 and the luma video signal component103. The chroma signal component 101 may be modulated at 3.58 megahertzand it may or may not comprise a constant chroma across the entire line.The luma signal component 103 may increase in amplitude in a stair stepfashion or it may not.

FIG. 2A is a diagram illustrating modulated chroma signals in contiguouscomposite video frames. The chroma component may be modulated so that afrequency of each successive line of video may be phase-shifted by 180degrees with respect to the previous line. Referring to FIG. 2A, theprevious frame 201 may comprise a previous line 203, a current line 205,and a next line 207. Similarly, the current frame 209 may comprise aprevious line 211, a current line 213, and a next line 215. The currentline 213 in the current frame 209 may be phase-shifted by 180 degreesfrom the previous line 211 in the current frame 209, as well as from thenext line 215 in the current frame 209. Similarly, the current line 205in the previous frame 201 may be phase-shifted by 180 degrees from theprevious line 203 in the previous frame 201, as well as from the nextline 207 in the previous frame 201. In addition, since frames in thecontiguous composite video signal are at a frequency rate of 59.94 Hz,there may be a 180-degree phase shift between two adjacent frames, forexample, the current frame 209 and the previous frame 201.Correspondingly, the current line 213 in the current frame may be 180degrees phase-shifted from the current line 205 in the previous frame201.

In conventional video processing, there are three ways to separate theluma and chroma video components and these include combing horizontally,combing vertically, and combing temporally. During separation of theluma and chroma components, there are three bandwidth directions thatmay incur losses in the separation process and in the separated signal.Depending on the combing method that is utilized, the separated signalmay have reduced vertical bandwidth, horizontal bandwidth, and/ortemporal bandwidth.

The first way to separate the luma and chroma-video components is byhorizontal combing. Horizontal combing may be accomplished by utilizinga notch filter, for example. Since the chroma signal component in acomposite video signal may be modulated at 3.58 MHz, a notch filter setat 3.58 MHz may be utilized. Combing vertically may also be utilized toseparate the luma and chroma video components. Combing vertically may beachieved in three different ways—the current line may be combed with theprevious and the next line, the current line may be combed with the linejust before it, or the current line may be combed with the line justafter it. The vertical combing is performed spatially, which involvescombing only within one field at a time and without any temporalcombing.

During combing in the current frame 209, for example, if the currentline 213 is added to the previous line 211, the chroma content maycancel out and two times the luma content may be obtained. On the otherhand, if the previous line 211 is subtracted from the current line 213,the luma content may cancel out and two times the chroma content may beobtained. In this way, luma and chroma content may be separated from thecomposite video signal for further processing. However, vertical combingmay result in a reduced vertical bandwidth.

A third way to comb a composite signal is to comb temporally. Combingtemporally comprises combing between two adjacent frames, for example,the current frame 209 and the previous frame 201. Further, temporalcombing may be characterized by a reduced temporal bandwidth. Luma andchroma content may be separated by utilizing the same addition andsubtraction method between a current line and a previous line as it wasutilized with vertical combing.

FIG. 2B is a diagram illustrating combing of a correlated current line224 and a previous line 222 in a current frame 220. In this case, thereis no vertical bandwidth and the previous line 222 and the current line224 are perfectly correlated. The current line 224 may be added with theprevious line 222 and two times luma may be obtained. Similarly, theprevious line 222 may be subtracted from the current line 224 so thattwo times chroma may be obtained.

FIG. 2C is a diagram illustrating combing of a non-correlated currentline 234 and a previous line 232 in a current frame 230. In this case,there may be significant vertical bandwidth. The vertical bandwidth maybe high enough so that there may be no correlation between the currentline 234 and the previous line 232. When the current line 234 and theprevious line 232 are combed together, there may be significant error inboth the luma and chroma. This may produce combing artifacts in theobtained combed video signal. A substantially the same result may beobtained when combing temporally when there is temporal bandwidth, whichindicates motion. Higher bandwidth in a given direction may causecombing in that direction to result in more incorrectly separated lumaand chroma.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

Certain aspects of the invention may be found in a method and system forcombing a video signal. A weight may be assigned to a 3D comb mesh valueand combing may be blended according to the assigned weight of the 3Dcomb mesh value. The weighted 3D comb mesh value may be accumulated inorder to generate an accumulated mesh value. If the accumulated meshvalue exceeds a saturation value, the accumulated mesh value may bereduced to the saturation value. If the 3D comb mesh value is smallerthan a first threshold value, the accumulated mesh value may be reset tozero. A multiplier may be generated according to the accumulated meshvalue. If the accumulated mesh value is between a second threshold valueand a third threshold value, the multiplier may be blended. Blending ofthe multiplier may be varied over a determined range between the secondthreshold value and the third threshold value. If the accumulated meshvalue is at most equal to the second threshold value, the multiplier maybe set to zero. If the accumulated mesh value is at least equal to thethird threshold value, the multiplier may be set to one. Combing may beblended according to the blended multiplier and the 3D comb mesh value.If the multiplier is zero, 3D combing may be disabled. If the multiplieris one, the video signal may be 3D combed according to the 3D comb meshvalue.

Another aspect of the invention may provide a machine-readable storage,having stored thereon, a computer program having at least one codesection executable by a machine, thereby causing the machine to performthe steps as described above for combing a video signal.

The system for combing a video signal may include at least one processorthat assigns a weight to a 3D comb mesh value and blends combingaccording to the assigned weight of the 3D comb mesh value. A firstcircuitry may accumulate the weighted 3D comb mesh value to generateaccumulated mesh value. If the accumulated mesh value exceeds asaturation value, second circuitry may reduce the accumulated mesh valueto the saturation value. If the 3D comb mesh value is smaller than afirst threshold value, reset circuitry may reset the accumulated meshvalue to zero. Third circuitry may generate a multiplier according tothe accumulated mesh value. If the accumulated mesh value is between asecond threshold value and a third threshold value, the third circuitrymay blend the multiplier. The third circuitry may vary blending over adetermined range between the second threshold value and the thirdthreshold value. If the accumulated mesh value is at most equal to thesecond threshold value, the third circuitry may set the multiplier tozero. If the accumulated mesh value is at least equal to the thirdthreshold value, the third circuitry may set the multiplier to one. Theprocessor may blend combing according to the blended multiplier and the3D comb mesh value. If the multiplier is zero, the processor may disable3D combing. If the multiplier is one, the processor may 3D combaccording to the 3D comb mesh value. The third circuitry may comprise anestimation circuitry. The second circuitry may comprise a saturationcircuitry. The first circuitry may comprise an adder.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating generation of a conventional compositevideo signal.

FIG. 2A is a diagram illustrating modulated chroma signals in contiguouscomposite video frames.

FIG. 2B is a diagram illustrating combing of a correlated current lineand a previous line in a current frame.

FIG. 2C is a diagram illustrating combing of a non-correlated currentline and a previous line in a current frame.

FIG. 3A is a diagram illustrating 2D and 3D comb filtering, inaccordance with an embodiment of the invention.

FIG. 3B is a diagram of a blending decision factor related to blendingto previous line versus blending to next line, in accordance with anembodiment of the invention.

FIG. 3C is a diagram of a blending decision factor related to blendingvertically versus blending horizontally, in accordance with anembodiment of the invention.

FIG. 3D is a diagram of a blending decision factor related to enablinghorizontal combing versus disabling horizontal combing, in accordancewith an embodiment of the invention.

FIG. 3E is a diagram of a blending decision factor related to horizontalcombing, in accordance with an embodiment of the invention.

FIG. 4A is a diagram of coarse luma determination, in accordance with anembodiment of the invention.

FIG. 4B is a diagram of a 3D comb filter mesh mask, in accordance withan embodiment of the invention.

FIG. 4C is a diagram of a 3D comb filter mesh mask, in accordance withan embodiment of the invention.

FIG. 4D is a diagram of a 3D comb filter mesh, in accordance with anembodiment of the invention.

FIG. 5 is a block diagram of a time constant calculation circuit, inaccordance with an embodiment of the invention.

FIG. 6 is a flow diagram of an exemplary method for 3D comb filter timeconstant determination, in accordance with an embodiment of theinvention.

FIG. 7 is a block diagram of an exemplary system that may be used inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain aspects of the invention may be found in a method and system forcombing a video signal. During separation of the chroma and luma signalcomponents, a 3D comb mesh value may be generated. The 3D comb value mayindicate, for example, to what extent a composite video signal may be 3Dand 2D combed. A 3D comb mesh value may be generated by a unidirectionalor bidirectional 3D comb filter. A unidirectional comb filter is morefully described in U.S. patent application Ser. No. 10/943,267, filedSep. 17, 2004, entitled “Method and System for 3D Comb Filtering of aVideo Signal,” which is incorporated herein in its entirety. Abidirectional comb filter is more fully described in U.S. patentapplication Ser. No. 10/943,593, filed Sep. 17, 2004, entitled “Methodand System for 3D Bidirectional Comb Filtering,” which is incorporatedherein in its entirety.

A weight may be assigned to the 3D comb mesh value and combing may beblended according to the assigned weight of the 3D comb mesh value. Theweighted 3D comb mesh value may be accumulated in an accumulator. If the3D comb mesh value is smaller than a determined first threshold, thenthe accumulator may be reset. Accumulated 3D comb mesh value from theaccumulator may not be allowed to exceed a saturation value S. If theaccumulated mesh value exceeds S, then the accumulated mesh value may beset to S. A multiplier may be generated according to the accumulatedmesh value. If the accumulated mesh value is at most a second threshold,then the multiplier may be set to zero and 3D combing may be disabled.If the accumulated mesh value is at least a third threshold, then themultiplier may be set to one and 3D combing may be allowed in accordancewith the 3D comb mesh value. If the accumulated mesh value is betweenthe second and third threshold values, the multiplier may be blended.The 3D comb mesh value may then be blended in accordance with theblended multiplier.

FIG. 3A is a diagram illustrating 2D and 3D comb filtering, inaccordance with an embodiment of the invention. Referring now to FIG.3A, there is illustrated a sample of pixels from three adjacent lines ina current frame 304, a current line 307, a previous line 305, and a nextline 309, as well as a same (current) line 311 but in a previous frame310. The subcarrier phase 301 of the incoming composite video signal maybe 3.58 MHz, and the incoming analog video signal may be digitized at 27MHz, for example. Since 3.58 MHz and 27 MHz are not multiples of eachother, there may not be an exact pixel sample every 3.58 MHz ofdigitized video signal that is aligned and in-phase. For example, it maybe difficult to compare the peak of a sine wave on the current line 307with the peak of a sine wave on the next line 309, since a pixel samplemay not be obtained at the 27 MHz frequency. The composite video signal,therefore, may be run through a filter that interpolates pixel samples303 at four times the frequency of the sub-carrier. For example, if thesubcarrier frequency is at 3.58 MHz, the pixel samples 303 may beinterpolated at 14.32 MHz.

Pixels A, B and C may be true sample pixels. However, all the remainingpixels to the left and to the right of the true sample pixels A, B andC, such as pixels BL, Br, AL, AL2, AL3, AL4, Ar, Ar2, Ar3, Ar4, CL, andCr, may be interpolated pixels. In a given line, each pixel may beshifted by a quarter subcarrier cycle from the adjacent pixel. Inaddition, each line may be 180 degree phase-shifted from its adjacentline. For example, pixel A and interpolated pixel AL4, to the left ofpixel A in the current line 307, may be in phase with each other,whereas pixel A and interpolated pixel AL may be quarter cyclephase-shifted from each other. Similarly, interpolated pixel Ar may be aquarter cycle phase-shifted to the right of pixel A, and interpolatedpixel Ar4 may be in phase with pixel A. Since the current line 307 maybe 180 degrees phase-shifted from either the previous line 305 or thenext line 309, pixel A may also be phase-shifted 180 degrees from eitherpixel B in the previous line 305 or pixel C in the next line 309.

In an embodiment of the present invention, the amount of frequencycontent movement may be approximated between pixels within a given pixelline, between pixel lines within the same video frame, and betweensimilar pixel lines in adjacent frames, and the corresponding combingmethod may be applied with a minimum bandwidth loss. For example, ifvertical combing is applied with regard to pixel A, then pixel A may besubtracted from pixel B resulting in two times the luma, or pixel A maybe subtracted from pixel C to obtain two times the luma, or pixel A maybe subtracted from the average of B and C to obtain two times the luma.The same process may be performed between pixel A and interpolated pixelAL2, since they are out of phase The phase difference between pixels Aand B is the same as between pixel A and interpolated pixel AL2, i.e.180 degrees. In order to determine whether vertical combing may beapplied without a significant bandwidth loss, pixels in the current line307 and the previous line 305 may be compared. For example, interpolatedpixel AL in the current line 307 may be compared with interpolated pixelBr in the previous line 305, where interpolated pixel AL is in phasewith interpolated pixel Br since there is 360 degree phase differencebetween them. Similarly, interpolated pixel Ar may be compared withinterpolated pixel BL, where interpolated pixel Ar is in phase withinterpolated pixel BL since there is 360 degrees phase differencebetween them as well.

If these two comparisons indicate a big difference, this may beindicative of significant vertical frequency content going from B to A.If the difference between the interpolated pixels in the two comparisonsis small, then this may indicate that there is not a lot of verticalfrequency content. Accordingly, vertical combing may be applied betweenthe current line 307 and the previous line 305 without a significantbandwidth loss. Similarly, comparisons between the interpolated pixelsAL and Cr, and Ar and CL may be indicative of whether vertical combingmay be applied between the current line 307 and the next line 309,without a significant bandwidth loss. Depending on the composite videosignal, there may be no frequency content between pixel B and pixel A,which indicates that the current line and the previous line areidentical lines. A large frequency content between pixel A and pixel Cmay indicate that a vertical transition has happened immediately afterthe current line. Conversely, there may be a lot of frequency contentbetween pixel B and pixel A, and no frequency content between pixel Aand pixel C. This may be characterized by the fact that the current lineand the next line are very similar, but the current line and theprevious line are different. In this case, vertical combing may beperformed between the current line and the next line.

A final comparison may be performed between pixels A, B and C, in orderto determine whether vertical combing may be applied with a minimumbandwidth loss. If pixels A, B and C are, for example, all in phase witheach other, this may be indicative that there is no chroma component andpixels A, B and C contain only luma components, for example, if thevideo signal comprises a white character or a black background. In thiscase, since there is no frequency content between the current line 307,the previous line 305 and the next line 309, vertical combing may beapplied without a significant loss in bandwidth.

With regard to horizontal combing, or notch filtering, pixel A may becompared with interpolated pixels AL4 and Ar4 in the current line 307,which are in phase with pixel A. This may provide an indication of thehorizontal frequency content in the current line 307. If pixel A is verydifferent from either of interpolated pixels AL4 or Ar4, it may indicatethat there is significant frequency content in the current line 307. If,on the other hand, the pixels are very similar, it may indicate thatthere is less frequency content and horizontal combing may be applied.In an embodiment of the present invention, a wide band pass filter maybe utilized in order to horizontally filter a composite signal andeliminate the luma component that is not near the chroma subcarrierfrequency, for example, a 3.58 MHz subcarrier frequency.

In yet a different embodiment of the present invention, 3D combing mayalso be implemented taking into consideration temporal signal comparisonfor purposes of applying temporal combing with a minimum temporalbandwidth loss. Referring again to FIG. 3A, pixels in the sameline/previous frame 311 may be considered. For example, GA may be anactual pixel similar to pixel A, but it may be phase-shifted 180 degreesfrom pixel A in the previous frame. Pixel GA may be the same pixel aspixel A in the previous frame, interpolated pixel GAL may be one quarterof a 3.58 MHz subcarrier frequency off to the left in theprevious-frame, and interpolated pixel GAR may be one-quarter of asubcarrier cycle off to the right on the same line in the previousframe. Since pixels Ar and GAL are phase-shifted at 360 degrees and arein phase with each other, they may be compared for temporal frequencycontent.

Similarly, pixels AL and GAR may also be compared for temporal frequencycontent. If these two comparisons indicate that the pixels are similar,then this may indicate that pixel A is very similar to pixel GA and thatthere is no temporal frequency content movement from the previous frame.In this case, temporal combing may be performed since there will be nosignificant temporal bandwidth loss. If, on the other hand, the twocomparisons show a large difference, then it may be indicative of asignificant temporal frequency content between the current and theprevious frame, and temporal combing, therefore, may not be desirablesince it may involve temporal bandwidth loss. A comparison between pixelA and pixel GA may be useful in instance where there is a pixel thatbears no color, for example, a black and/or a white pixel. Such pixelsare characterized only by a luma component and, therefore, have no phasedifference between each other. In this case, temporal combing may beapplied without any resulting temporal bandwidth loss.

A 3D comb filter in accordance with an embodiment of the presentinvention, may be implemented by first horizontally combing a compositevideo signal. The horizontal combing may be accomplished by running thecomposite video signal through a very wide band pass filter, forexample, so that it may pre-filter the very low frequency luma componentwithin the composite video signal. In this way, if there is very coarse(VC), slow moving luma changes, such VC luma may be eliminated and notbe considered in subsequent vertical and/or temporal combing processes.If a subcarrier frequency of 3.58 MHz is utilized, chroma components maybe centered around 3.58 MHz, or approximately between 2 and 5 MHz. Inother words, any frequency content below 2 MHz may be considered a lumacomponent and may be filtered out by the band pass filter. By performingthe corresponding comparisons between pixels, as outlined above, it maybe determined whether vertical combing and/or temporal combing may beutilized without significant bandwidth loss. For example, horizontal andvertical combing, or 2D combing, may be the only useful combing methodsin one embodiment of the present invention. In another embodiment of thepresent invention, horizontal, vertical and temporal combing, or 3Dcombing, may be applied without significant bandwidth loss. A finalcombing decision as to a specific composite signal may include a blendof 2D and 3D combing. In this case, a certain percentage of a pixel maybe only vertically or horizontally combed, and the remaining percentageof the pixel may be combed vertically and temporally.

FIG. 3B is a diagram 330 of a blending decision factor related toblending to previous line versus blending to next line, in accordancewith an embodiment of the invention. Referring to FIG. 3B, a decision asto the quality of combing with the previous line versus combing with thenext line may be accomplished by calculating a ratio k_blend of theprevious line compares to the next line compares, for example. Thek_blend ratio may be calculated using compares and constant multipliesso that it is a value between zero and one. This is a non-linear ratiobetween the comparison to the previous line and the comparison to thenext line. A constant value in the k_blend calculation may be utilizedto bias strongly against luma only comparisons. In the case of lowchroma it may not be desirable to falsely pass the luma only condition.K_blend may be calculated as a function of next_max and prev_max.Next_max may be a measure of the bandwidth difference between a currentline and a next line, for example. Prev_max may be a measure of thebandwidth difference between a current line and a previous line, forexample. K_blend may be a function of the ratio of prev_max to next_max.The larger the ratio, the smaller the value of k_blend. The previous andnext lines may be alpha blended together to comb with the current line.Conceptually the blend tends toward the smaller of prev and next. Theblend will skew toward next_line when next_max/prev_max is small, andskew toward prev_line when prev_max/next_max is small.

In one-aspect of the invention, a different blending decision factor maybe determined. A notch filter may be utilized for horizontal combing. Inorder to obtain a better combing decision, a notch filter may becompared to a vertical comb filter by calculating a ratio of the qualityof the vertical comb using the previous line, to the quality of thehorizontal comb. A different ratio my be related to the quality of thevertical comb using the next line, to the quality of the horizontalcomb.

FIG. 3C is a diagram 340 of a blending decision factor related toblending vertically versus blending horizontally, in accordance with anembodiment of the invention. Referring now to FIG. 3C, a blendingdecision factor may be determined from a ratio notch_prev, wherenotch_prev may indicate whether to blend vertically and/or horizontallybetween a current line and a previous line. Notch_prev may be determinedas a function of prev_line_max and next_pix_max. Prev_line_max may be ameasure of the bandwidth difference between a current line and aprevious line. Next_pix_max may be a measure of the bandwidth differencebetween two sets of in-phase pixels in a current line. A highernotch_prev ratio may indicate a preference towards notching versusvertical blending.

A notch_next ratio may be determined in a similar way, where notch_nextmay indicate whether to blend vertically and/or horizontally between acurrent line and a next line. A final notch ratio may be determined as afunction of the notch_prev and notch_next ratios in order to obtain ablending decision factor related to blending vertically versus blendinghorizontally. For example, a final notch value for each pixel may bedetermined by the following equation:notch=notch_next.*k_blend+notch_prev.*(1−k_blend)

Conceptually, if the k_blend combing decision tends towards combing withthe top line, the top line may be given more weight in judging therelative goodness of notching. If the k_blend combing decision tendstowards combing with the bottom line, the bottom line may be given moreweight in judging the relative goodness of notching.

In cases of significantly more luma than chroma at a given point in acomposite signal, a notch filter may be gradually disabled. This isbecause the notch filter tends to put most of the signal that is left,after an initial high pass filter, into chroma. If the combed signal ismostly luma, it may be inefficient to allow it to be put into chroma.

FIG. 3D is a diagram 350 of a blending decision factor related toenabling horizontal combing versus disabling horizontal combing, inaccordance with an embodiment of the invention. Referring to FIG. 3D, adisable notch signal dis_notch_prev may be generated by a ratio of theprevious/next line compare with the previous/next line luma onlycompare. If the point is mostly luma, the luma only compare will be muchsmaller than the in phase compare. Dis_notch_prev may be determined as aratio between prev_line_min and same_pix_max, for example. Prev_line_minmay be associated with a bandwidth difference between in-phase pixels ina current and previous lines. Same_pix_max may be associated with abandwidth difference between out-of-phase pixels in a current, previousand next line.

Similarly, a dis_notch_next may be determined as a ratio betweennext_line_min and same_pix_max, for example, where next_line_min may beassociated with a bandwidth difference between in-phase pixels in acurrent and next lines. Dis_notch_next and dis_notch_prev, therefore,may be determined by the ratio of the previous or next line luma andchroma compare to the previous or next line luma only compare.

If the amplitude of the band passed video signal is very small relativeto the difference to the closest matching adjacent line, then thedisable notch parameter is not an accurate measure. In this case, thedisable notch may not be used. A disable vertical notch, dis_vert_notch,parameter may be utilized.

FIG. 3E is a diagram 360 of a blending decision factor related tohorizontal combing, in accordance with an embodiment of the invention.Referring now to FIG. 3E, a dis_vert_notch may be calculated as a ratioof notch_a_abs_filt and min_vert, for example. Notch_a_abs_filt maymeasure the absolute value of an amplitude of a signal on a currentline. Min_vert may be associated with the minimum of bandwidthdifference between current line and a previous line, and/or a currentline and a next line.

Conceptually, if dis_vert_notch is zero, then it has no effect.Dis_notch is allowed to mask or not mask notch. If dis_vert_notch isone, then dis_notch has no effect and dis_notch may be disabled. In thiscase notch is never masked, and the decision to notch or vertically combis utilized without modification. A weighted disable notch ratiodis_notch may be calculated as:dis_notch=max(dis_notch, dis_vert_notch)

The calculated notch signal may be cubed and disable notch may besquared. This may cause the roll off due to notch to be accelerated.Then disable notch may be used to calculate a final value for notching.Notch may also be low pass filtered and may be generated according tothe following equation:notch=dis_notch^2*notch^3

Referring again to FIG. 3A, since points A and GA are 180 degrees out ofphase with each other, in chroma, they may not be directly compared,except in the case where there is no chroma at this point. Points A, B,C and G are actual sampled points sampled at 27 MHz. All the otherpoints may be interpolated to give 4FSC sample points. Points AL and ARmay be one quarter of a subcarrier cycle away from point A. Points GALand GAR may be one quarter of a subcarrier cycle away from point GA.Since points A and GA may be 180 degrees out of phase with each other,AL may be in phase with GAR and AR may be in phase with GAL. Since theyare in phase they can be directly compared. There may be some spatialdifference between these points and points A and GA. But, by shiftingthe samples a quarter of a cycle in each direction, the spatialdifference may be minimized a measure of the temporal bandwidth(motion). In order to calculate a measure of temporal bandwidth, in thecase where there is no chroma at this point, points G may be compareddirectly with point A. The actual measure of the temporal bandwidth maybe calculated by comparing the temporal bandwidth in the case Withchroma and the case of luma only. The results may be low pass filtered.

An estimate may be obtained of the quality of the 2D comb. This may becalculated based on the difference between the current pixel and thepixel that the 2D combing logic decided to comb with. First the verticaldifference may be calculated according to the ratio of k_blend. Nextthis may be blended with the horizontal quality according to the ratioof notch. The qualities of the vertical blends, previous and next, maybe weighted together to give an overall vertical quality measure. Thisvertical quality measure may then be weighted together with thehorizontal quality, giving an overall quality measure of the 2D comb.

FIG. 4A is a diagram 400 of coarse luma determination, in accordancewith an embodiment of the invention. A coarse estimate of luma may beobtained for both the current frame and the previous frame asillustrated in FIG. 4A. This may be accomplished by subtracting the bandpassed signal from the composite signal. In this way, the part of lumathat is clearly outside the chroma bandwidth range may be obtained. Thecoarse estimate of luma may be used to mask off the 3D combing decision.If the luma part of the composite signal does not match between the twoframes, it may be determined that there is motion. This may be true evenif the band passed part of the signal matches perfectly.

FIG. 4B is a diagram 410 of a 3D comb filter mesh mask, in accordancewith an embodiment of the invention. A mesh mask may be utilized inorder to ascertain whether 3D combing may be utilized for a specificcomposite signal. Referring now to FIGS. 4A and 4B, the output of a wideband pass filter may be subtracted from an original composite signalinput, and a low frequency luma component may be obtained, or a roughestimate of the low frequency luma. Such estimate of low frequency lumamay be calculated for a current frame and for a previous frame, forexample. The two resulting rough values of luma may then be compared ona pixel-by-pixel basis. If the two rough luma values are very different,then 3D combing may be disabled by the mask, at 401, and 2D combing bethe only method that may be applied to separate luma and chromacomponents in the composite video signal. If the two rough luma valuesare very similar, then 3D combing may be allowed by the mesh mask, at403, and the composite video signal may be combed horizontally,vertically and temporally. For any value of the luma difference, whichis between 401 and 403, a blended mask 405 may be applied to separatethe luma and chroma components of the composite video signal.

In another embodiment of the present invention, the blended mask 405 maybe applied in cases where the two rough luma values are not verydifferent. A blended mask may indicate, for example, that a certainpercentage of the 3D combing, for example 30%, may be “trusted” and theremaining percent, for example the remaining 70%, may be combed via 2Dcombing. The blended mask may re-adjust the ratio between 3D combing and2D combing for a given pixel depending on how close the two rough lumavalues are to being very different and how close they are to being verysimilar.

FIG. 4C is a diagram 420 of a 3D comb filter mesh mask, in accordancewith an embodiment of the invention. Mesh_mask may be determined as aratio between coarse_minus and coarse_plus, for example. Coarse_minusmay be the difference between lumas of previous and current frames.Coarse_plus may be the sum of lumas of previous and current frames.Mesh_mask ratio may tend towards masking 3D combing if the luma betweenthe two consecutive frames is very different. It may also tend towardsallowing 3D combing if the luma between the two consecutive frames isvery similar.

FIG. 4D is a diagram 430 of a 3D comb filter mesh, in accordance with anembodiment of the invention. Referring to FIG. 4D, a mesh ratio may bedetermined as a measure of combing quality of 2D combing versus 3Dcombing. Mesh may be determined as a ratio betweenprev_field_max_filt_(—)3d and quality_(—)2d. Prev_field_max_filt_(—)3dmay be a measure of bandwidth difference between a pixel in a currentframe and the same pixel in a previous frame. Quality_(—)2d may be ameasure of quality of 2D combing, as measured, for example, by variousratios as specified above in this application.

To determine the blending of 3D combing versus 2D combing the quality ofthe 2D comb decision is compared with the quality of 3D combing. Theratio of these two numbers determines the blend between 2D and 3Dcombing. Conceptually, mesh may tend towards the smaller ofquality_(—)2d (error term of 2D comb) and prev_field_max_filt_(—)3d(error term of, 3D comb). The larger prev_field_max_filt_(—)3d is (orthe worse the quality of the 3D comb), the more mesh may tend to 2Dcomb. The larger quality_(—)2d (or the worse the quality of the 2Dcomb), the more mesh may tend to 3D comb.

A final blend of 3D combing and 2D combing may be based on the productof the mesh and the mesh mask. The following equation may be utilized:mesh=mesh*mesh_maskThe final mesh value may be used to alpha blend the chroma and lumabetween 2D and 3D combing.

In yet a different embodiment of the present invention, a time constantmay be utilized to attenuate, or affirm, a 3D comb filter mesh value fora current frame based on 3D comb filter mesh values of preceding frames.For example, if the 3D comb filter mesh values of the preceding framesallow for 3D combing, then the time constant may be utilized to affirmthe current 3D comb filter mesh value and allow for 3D combing in thecurrent frame. Similarly, if the 3D comb filter mesh value of thepreceding frames indicate that 2D combing, rather than 3D combing, maybe utilized for minimum bandwidth loss, then the time constant may beutilized to attenuate the 3D comb filter mesh value thus indicating ahigher likelihood for 2D combing in the current frame. A 3D mesh valuemay be generated by a unidirectional or bidirectional 3D comb filter,for example.

FIG. 5 is a block diagram of a time constant calculation circuit, inaccordance with an embodiment of the invention. The time constantcalculation circuit 500 may comprise a mesh input block 501, anaccumulator 511, a saturation circuit 515, a reset circuit 512, amultiplier circuit 519, and a multiplier 523.

In operation, the mesh input block 501 may be adapted to provide a 3Dcomb filter mesh value received from a unidirectional or a bidirectional3D comb filter, for example. Each received 3D mesh value may be comparedto threshold values 503. For example, threshold values K₁, K₂, and K_(n)may be utilized. The threshold values K₁, K₂, and K_(n) may beassociated with multipliers 505, M₁, M₂, and M_(n), respectively, sothat if a threshold value is satisfied, the corresponding thresholdmultiplier may be applied to the mesh value. After a multiplier isapplied to a mesh value, the result may be stored in the accumulator511. The threshold value K_(off) may be associated with an accumulatorreset function. If a 3D comb mesh value generated by the mesh inputblock 501 is smaller than the threshold K_(off), the accumulator 511 maybe reset by the reset circuit 512.

The saturation circuit 515 may be adapted to accumulate the receivedmesh values for each frame and saturate at a predetermined value S. Forexample, five subsequent 3D comb mesh values may indicate 3D combing andmay saturate the saturation circuit 515. After a weighted mesh value isstored in the accumulator 511, a mesh enable value (mesh_enb) may becommunicated to the mesh multiplier estimation block 519. Mesh_enb maybe equal to the weighted mesh value stored in the accumulator 511.

The multiplier circuit 519 may be adapted to calculate a mesh multipliervalue based on the mesh enable value, where the mesh multiplier valuemay be between zero and one. For example, the multiplier circuit 519 maydetermine whether the mesh enable value is a value between a lowerthreshold T1 and a higher threshold T2. The values of lower threshold T1and a higher threshold T2 may be determined for different embodiments ofthe present invention and may be programmable. If mesh_enb is at mostthe threshold T1, then the multiplier circuit 519 may return a zerovalue for the mesh multiplier value. Similarly, if mesh_enb is higherthan the threshold T2, then the multiplier circuit 519 may return avalue of one for the mesh multiplier value. If mesh_enb is between thethreshold T1 and T2, then the multiplier circuit 519 may blend the meshmultiplier and may return a value between zero and one for the meshmultiplier value. The mesh multiplier value may then be communicated tothe multiplier 523, where the current 3D mesh value received from themesh input block 501 and the mesh multiplier value are multiplied. Themesh multiplier value, therefore, may be utilized as a 3D comb filtertime constant as it attenuates, or affirms, a 3D comb filter mask for acurrent frame based on 3D comb filter mask values of preceding frames.In this way, if the mesh multiplier is zero, final 3D comb mesh value525 will be zero and as a result 3D combing will be disabled. If themesh multiplier is one, final 3D comb mesh value 525 will be equal tothe initial 3D comb mesh value received from the mesh input block 501.In this way, 3D combing will be performed in accordance with theoriginal 3D comb mesh value.

In another aspect of the invention, a mesh multiplier value, or a timeconstant value, may be determined by utilizing the following exemplarycode:

-   The equation add_to_enb=(mesh>K₁)*M₁+(mesh>K₂)*M₂+(mesh>K_(n))*M_(n)    represents the assigning of weight to a 3D comb mesh value by    utilizing the multipliers 505, M₁, M₂, and M_(n), if the 3D comb    mesh value is greater than the threshold values K₁, K₂, and K_(n),    respectively.-   The equation mesh_enb=(mesh_enb+add_to_enb)*(mesh>K_(off))    represents the accumulation of the weighted 3D comb mesh values and    resetting of the accumulation if the 3D comb mesh value is smaller    than the threshold value K_(off).-   The equation mesh_enb=min(mesh_enb, 16) represents the saturation of    mesh_enb that may be utilized in a saturation block, for example. A    saturation value of S=16 is utilized in this example, but the    invention is not limited in this way. In another aspect of the    invention, other saturation values may be utilized.-   The equation mesh_mult=max(0, mesh_enb−8)/8 represents blending of a    mesh multiplier, that may be utilized in a multiplier circuit, for    example. Subtraction and dividing by a factor of 8 may be utilized    to achieve the blending. The factor 8 is selected to correspond to    the saturation value S=16, but the invention is not limited in this    way. In another aspect of the invention, other subtraction and    divide factors that correspond to the saturation value may be    selected.-   The equation mesh=mesh*mesh_mult represents the final blending of    the 3D comb mesh value utilizing the blended mesh multiplier value.

FIG. 6 is a flow diagram of an exemplary method 600 for 3D comb filtertime constant determination, in accordance with an embodiment of thepresent invention. At 601, a 3D comb mesh value (CMV) may be obtained.At 603, weight may be assigned to the CMV. For example, a plurality ofmultipliers may be utilized depending on the value of the CMV. At 605,the weighted CMV may be stored in an accumulator. At 607 it may bedetermined whether the CMV is smaller than a first threshold value. Ifthe CMV is smaller than a first threshold value, the accumulator storingthe weighted CMV may be reset at 609. At 611 it may be determinedwhether the accumulated CMV is greater than a saturation value S. If theCMV is greater than the saturation value S, then, at 613, theaccumulated CMV may be set to the saturation value S. At 615, amultiplier may be generated according-to the accumulated CMV.

At 617, it may be determined whether the accumulated CMV is at mostequal to a second threshold value. If the accumulated CMV is at mostequal to the second threshold value, at 619, the multiplier may be setto zero and 3D combing may be disabled, at 621. At 623, it may bedetermined whether the accumulated CMV is at least equal to a thirdthreshold value. If the accumulated CMV is at least equal to the thirdthreshold value, at 629, the multiplier may be set to one and 3D combingmay be performed according to the original 3D comb mesh value, at 631.At 625, the multiplier may be blended over a determined range betweenthe second and third threshold values. At 627, combing may be blendedaccording to the blended multiplier and the 3D comb mesh value.

FIG. 7 is a block diagram of an exemplary system that may be used inaccordance with an embodiment of the invention. Referring now to FIG. 7,the system 700 may comprise a host 701 and a comb filter 703. The host701 may comprise a processor 705 and a host memory 707. The host 701 maybe communicatively coupled to the comb filter 703 via an interface bus715. In another embodiment of the present invention, the comb filter 703may be a part of the host 701. The comb filter 703 may comprise aunidirectional or a bidirectional comb filter, for example.

In operation, the comb filter 703 may comprise suitable logic, circuitryand/or code and may be adapted to receive a video signal 709, separatethe chroma and luma components, and then output the chroma component 711and the luma component 713 separately. In addition, the comb 703 may beadapted to generate a 3D comb mesh value. The 3D comb value mayindicate, for example, to what extent a composite video signal may be 3Dand 2D combed. The processor 705 may be adapted to assign a weight to a3D comb mesh value and may blend combing according to the assignedweight of the 3D comb mesh value. A first accumulating circuitry mayaccumulate the weighted 3D comb mesh value to generate accumulated meshvalue. If the accumulated mesh value exceeds a saturation value, secondcircuitry may reduce the accumulated mesh value to the saturation value.If the 3D comb mesh value is smaller than a first threshold value, areset circuitry may reset the accumulated mesh value to zero. Thirdcircuitry may generate a multiplier according to the accumulated meshvalue. If the accumulated mesh value is between a second threshold valueand a third threshold value, the third circuitry may blend themultiplier. The third circuitry may vary blending over a determinedrange between the second threshold value and the third threshold value.If the accumulated mesh value is at most equal to the second thresholdvalue, the third circuitry may set the multiplier to zero. If theaccumulated mesh value is at least equal to the third threshold value,the third circuitry may set the multiplier to one. The processor 705 mayblend combing according to the blended multiplier and the 3D comb meshvalue. If the multiplier is zero, the processor 705 may disable 3Dcombing. If the multiplier is one, the processor 705 may 3D combaccording to the 3D comb mesh value. The third circuitry may comprise anestimation circuitry. The second circuitry may comprise a saturationcircuitry. The first circuitry may comprise an adder.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system, or in a distributed fashion where different elementsare spread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method for combing a video signal, the method comprising: assigninga weight to a 3D comb mesh value, wherein said 3D comb mesh valueindicates whether 3D combing may be used for combing the video signal;and blending 2D combing and 3D combing according to the assigned weightof the 3D comb mesh value.
 2. The method according to claim 1,comprising accumulating the weighted 3D comb mesh value to generateaccumulated mesh value.
 3. The method according to claim 2, comprisingreducing the accumulated mesh value to a saturation value, if theaccumulated mesh value exceeds the saturation value.
 4. The methodaccording to claim 2, comprising resetting the accumulated mesh value tozero, if the 3D comb mesh value is smaller than a first threshold value.5. The method according to claim 2, comprising generating a multiplieraccording to the accumulated mesh value.
 6. The method according toclaim 5, comprising blending the multiplier, if the accumulated meshvalue is between a second threshold value and a third threshold value.7. The method according to claim 6, comprising varying blending over adetermined range between the second threshold value and the thirdthreshold value.
 8. The method according to claim 6, comprising settingthe multiplier to zero, if the accumulated mesh value is at most equalto the second threshold value.
 9. The method according to claim 6,comprising setting the multiplier to one, if the accumulated mesh valueis at least equal to the third threshold value.
 10. The method accordingto claim 6, comprising blending combing according to the blendedmultiplier and the 3D comb mesh value.
 11. The method according to claim5, comprising disabling 3D combing, if the multiplier is zero.
 12. Themethod according to claim 5, comprising 3D combing according to the 3Dcomb mesh value, if the multiplier is one.
 13. A machine-readablestorage having stored thereon, a computer program having at least onecode section for combing a video signal, the at least one code sectionbeing executable by a machine for causing the machine to perform stepscomprising: assigning a weight to a 3D comb mesh value wherein said 3Dcomb mesh value indicates whether 3D combing may be used for combing thevideo signal; and blending 2D combing and 3D combing according to theassigned weight of the 3D comb mesh value.
 14. The machine-readablestorage according to claim 13, comprising code for accumulating theweighted 3D comb mesh value to generate accumulated mesh value.
 15. Themachine-readable storage according to claim 14, comprising code forreducing the accumulated mesh value to a saturation value, if theaccumulated mesh value exceeds the saturation value.
 16. Themachine-readable storage according to claim 14, comprising code forresetting the accumulated mesh value to zero, if the 3D comb mesh valueis smaller than a first threshold value.
 17. The machine-readablestorage according to claim 14, comprising code for generating amultiplier according to the accumulated mesh value.
 18. Themachine-readable storage according to claim 17, comprising code forblending the multiplier, if the accumulated mesh value is between asecond threshold value and a third threshold value.
 19. Themachine-readable storage according to claim 18, comprising code forvarying blending over a determined range between the second thresholdvalue and the third threshold value.
 20. The machine-readable storageaccording to claim 18, comprising code for setting the multiplier tozero, if the accumulated mesh value is at most equal to the secondthreshold value.
 21. The machine-readable storage according to claim 18,comprising code for setting the multiplier to one, if the accumulatedmesh value is at least equal to the third threshold value.
 22. Themachine-readable storage according to claim 18, comprising code forblending combing according to the blended multiplier and the 3D combmesh value.
 23. The machine-readable storage according to claim 17,comprising code for disabling 3D combing, if the multiplier is zero. 24.The machine-readable storage according to claim 17, comprising code for3D combing according to the 3D comb mesh value, if the multiplier isone.
 25. A system for combing a video signal, the system comprising: atleast one processor that assigns a weight to a 3D comb mesh value,wherein said 3D comb mesh value indicates whether 3D combing may be usedfor combing the video signal; and the at least one processor blends 2Dcombing and 3D combing according to the assigned weight of the 3D combmesh value.
 26. The system according to claim 25, comprising firstcircuitry that accumulates the weighted 3D comb mesh value to generateaccumulated mesh value.
 27. The system according to claim 26, comprisingsecond circuitry that reduces the accumulated mesh value to a saturationvalue, if the accumulated mesh value exceeds the saturation value. 28.The system according to claim 26, comprising reset circuitry that resetsthe accumulated mesh value to zero, if the 3D comb mesh value is smallerthan a first threshold value.
 29. The system according to claim 26,comprising a third circuitry that generates a multiplier according tothe accumulated mesh value.
 30. The system according to claim 29,wherein the third circuitry blends the multiplier, if the accumulatedmesh value is between a second threshold value and a third thresholdvalue.
 31. The system according to claim 30, wherein the third circuitryvaries blending over a determined range between the second thresholdvalue and the third threshold value.
 32. The system according to claim30, wherein the third circuitry sets the multiplier to zero, if theaccumulated mesh value is at most equal to the second threshold value.33. The system according to claim 30, wherein the third circuitry setsthe multiplier to one, if the accumulated mesh value is at least equalto the third threshold value.
 34. The system according to claim 30,wherein the at least one processor blends combing according to theblended multiplier and the 3D comb mesh value.
 35. The system accordingto claim 29, wherein the at least one processor disables 3D combing, ifthe multiplier is zero.
 36. The system according to claim 29, whereinthe at least one processor 3D combs according to the 3D comb mesh value,if the multiplier is one.
 37. The system according to claim 29, whereinthe third circuitry comprises an estimation circuitry.
 38. The systemaccording to claim 27, wherein the second circuitry comprises asaturation circuitry.
 39. The system according to claim 26, wherein thefirst circuitry comprises an adder.
 40. A method for combing a videosignal, the method comprising: assigning a weight to a 3D comb meshvalue, wherein said 3D comb mesh value indicates whether 3D combing maybe used for combing the video signal; blending 2D combing and 3D combingaccording to the assigned weight of the 3D comb mesh value; andaccumulating the weighted 3D comb mesh value to generate accumulatedmesh value.
 41. The method according to claim 40, comprising reducingthe accumulated mesh value to a saturation value, if the accumulatedmesh value exceeds the saturation value.
 42. The method according toclaim 40, comprising resetting the accumulated mesh value to zero, ifthe 3D comb mesh value is smaller than a first threshold value.
 43. Themethod according to claim 40, comprising generating a multiplieraccording to the accumulated mesh value.
 44. The method according toclaim 43, comprising blending the multiplier, if the accumulated meshvalue is between a second threshold value and a third threshold value.45. The method according to claim 44, comprising varying blending over adetermined range between the second threshold value and the thirdthreshold value.
 46. The method according to claim 44, comprisingsetting the multiplier to zero, if the accumulated mesh value is at mostequal to the second threshold value.
 47. The method according to claim44, comprising setting the multiplier to one, if the accumulated meshvalue is at least equal to the third threshold value.
 48. The methodaccording to claim 44, comprising blending combing according to theblended multiplier and the 3D comb mesh value.
 49. The method accordingto claim 43, comprising disabling 3D combing, if the multiplier is zero.50. The method according to claim 43, comprising 3D combing according tothe 3D comb mesh value, if the multiplier is one.
 51. A machine-readablestorage having stored thereon, a computer program having at least onecode section for combing a video signal, the at least one code sectionbeing executable by a machine for causing the machine to perform stepscomprising: assigning a weight to a 3D comb mesh value, wherein said 3Dcomb mesh value indicates whether 3D combing may be used for combing thevideo signal; blending 2D combing and 3D combing according to theassigned weight of the 3D comb mesh value; and accumulating the weighted3D comb mesh value to generate accumulated mesh value.
 52. Themachine-readable storage according to claim 51, comprising code forreducing the accumulated mesh value to a saturation value, if theaccumulated mesh value exceeds the saturation value.
 53. Themachine-readable storage according to claim 51, comprising code forresetting the accumulated mesh value to zero, if the 3D comb mesh valueis smaller than a first threshold value.
 54. The machine-readablestorage according to claim 51, comprising code for generating amultiplier according to the accumulated mesh value.
 55. Themachine-readable storage according to claim 54, comprising code forblending the multiplier, if the accumulated mesh value is between asecond threshold value and a third threshold value.
 56. Themachine-readable storage according to claim 55, comprising code forvarying blending over a determined range between the second thresholdvalue and the third threshold value.
 57. The machine-readable storageaccording to claim 55, comprising code for setting the multiplier tozero, if the accumulated mesh value is at most equal to the secondthreshold value.
 58. The machine-readable storage according to claim 55,comprising code for setting the multiplier to one, if the accumulatedmesh value is at least equal to the third threshold value.
 59. Themachine-readable storage according to claim 55, comprising code forblending combing according to the blended multiplier and the 3D combmesh value.
 60. The machine-readable storage according to claim 54,comprising code for disabling 3D combing, if the multiplier is zero. 61.The machine-readable storage according to claim 54, comprising code for3D combing according to the 3D comb mesh value, if the multiplier isone.
 62. A system for combing a video signal, the system comprising: atleast one processor that assigns a weight to a 3D comb mesh value,wherein said 3D comb mesh value indicates whether 3D combing may be usedfor combing the video signal; the at least one processor blends 2Dcombing and 3D combing according to the assigned weight of the 3D combmesh value; and first circuitry that accumulates the weighted 3D combmesh value to generate accumulated mesh value.
 63. The system accordingto claim 62, comprising second circuitry that reduces the accumulatedmesh value to a saturation value, if the accumulated mesh value exceedsthe saturation value.
 64. The system according to claim 62, comprisingreset circuitry that resets the accumulated mesh value to zero, if the3D comb mesh value is smaller than a first threshold value.
 65. Thesystem according to claim 62, comprising a third circuitry thatgenerates a multiplier according to the accumulated mesh value.
 66. Thesystem according to claim 65, wherein the third circuitry blends themultiplier, if the accumulated mesh value is between a second thresholdvalue and a third threshold value.
 67. The system according to claim 66,wherein the third circuitry varies blending over a determined rangebetween the second threshold value and the third threshold value. 68.The system according to claim 66, wherein the third circuitry sets themultiplier to zero, if the accumulated mesh value is at most equal tothe second threshold value.
 69. The system according to claim 66,wherein the third circuitry sets the multiplier to one, if theaccumulated mesh value is at least equal to the third threshold value.70. The system according to claim 66, wherein the at least one processorblends combing according to the blended multiplier and the 3D comb meshvalue.
 71. The system according to claim 65, wherein the at least oneprocessor disables 3D combing, if the multiplier is zero.
 72. The systemaccording to claim 65, wherein the at least one processor 3D combsaccording to the 3D comb mesh value, if the multiplier is one.
 73. Thesystem according to claim 65, wherein the third circuitry comprises anestimation circuitry.
 74. The system according to claim 63, wherein thesecond circuitry comprises a saturation circuitry.
 75. The systemaccording to claim 62, wherein the first circuitry comprises an adder.